Earth`s Ozone Layer Thinning At An Alarming Rate, Nasa Says

October 20, 1986|By Knight-Ridder Newspapers.

GREENBELT, MD. — The ozone layer, which protects life on Earth from deadly ultraviolet radiation, may be decaying up to eight times more rapidly than earlier projections predicted, according to new findings by the National Aeronautics and Space Administration.

The new studies by Donald Heath, a scientist at NASA`s Goddard Space Flight Center here, show that the ozone layer thinned worldwide from 1978 to 1984 by an average of about 3 percent. Over much of the United States and Europe, the ozone layer diminished about 2 percent during that time.

Scientists say the findings, based on an analysis of data collected since 1978 by a satellite orbiting 570 miles above Earth, are totally unexpected. They are worried because they do not understand why the decline has happened or whether it will get worse.

NASA scientists have begun reanalyzing other satellite data to see whether the information agrees with Heath`s findings. They say they have no reason to believe that either the satellite`s instruments were working improperly or that Heath`s analysis is incorrect.

``This is a great scientific mystery,`` said Richard Stolarski, a Goddard physicist.

Scientists say a decline in the ozone layer allows more ultraviolet radiation to reach Earth. Increased ultraviolet radiation has been linked to increases in skin cancer and cataracts, smog, crop damage, global warming, disruptions of aquatic life and possible damage to the body`s immune system.

Each percentage point of decrease in the amount of ozone could mean almost 200,000 additional skin-cancer cases worldwide each year, according to the Environmental Protection Agency.

Ozone, an unstable form of oxygen, is found in the stratosphere, roughly 12 to 30 miles above Earth`s surface. Scientists believe the ozone layer prevents about 90 percent of the sun`s ultraviolet rays from reaching Earth`s surface.

``This is an extremely serious environmental issue,`` said Robert Watson, the head of NASA`s upper-atmosphere research program in Washington. ``We had expected to see the ozone drop 3 to 10 percent over the next 100 years. But now we`ve seen a drop of about 3 percent during the period of only six years. This is a huge change, and we don`t yet understand why it is happening.``

Recent findings have reopened the debate that raged in the 1970s over threats to the ozone layer.

The National Science Foundation is so concerned about deterioration of the ozone layer over Antarctica that it sent a team of 13 scientists in August --in the heart of the continent`s dark winter--to try to find the cause. They are expected to announce their preliminary findings this week.

Among other recent scientific findings:

-- A large ``hole`` in the ozone layer, roughly the size of the United States and centered over the South Pole, has appeared over Antarctica each September and October and then gradually disappeared in November.

-- Heath has observed a smaller hole over the Arctic, about one-third the size of the Antarctic hole and centered over Spitsbergen, Norway, about 700 miles from the North Pole.

-- F. Sherwood Rowland, a chemistry professor at the University of California at Irvine who first suggested in 1974 that man-made chemicals could damage the ozone layer, said Friday that data from a scientific station in Arosa, Switzerland, had shown a drop of 3 percent in the ozone layer during the last decade. This is the first data from ground-based instruments to support Heath`s satellite data, he said.

British scientists first announced the discovery of the Antarctic hole in May, 1985. Their findings prompted further studies by scientists, who have offered three major explanations about its cause.

One theory blames man-made chemicals, such as chlorofluorocarbons (CFCs). Rowland and Mario Molina, Rowland`s colleague at the University of California in the early 1970s, found that CFCs drift into the stratosphere. The sun`s ultraviolet rays cause them to release chlorine, which then destroys ozone molecules.

CFCs are used in refrigerators, air conditioners, Styrofoam cups, insulation, solvents and other products. In 1978, the federal government banned the use of CFCs in spray cans. In 1980 the EPA proposed restricting CFCs in other products, but that proposal was abandoned when the Reagan administration took office.

Another theory holds that changes in the amount of ultraviolet rays emitted by the sun during the 11-year solar cycle are responsible. This theory says that increased ultraviolet radiation acts as a catalyst on nitrogen oxides emitted from burning fossil fuels.

A third theory suggests that recent global events, such as the 1982 eruption of the El Chichon volcano in Mexico, which spewed large amounts of sulfur and other chemicals into the upper atmosphere, may play a role.